Abstracts

Rationale: Autonomic dysfunction during seizures is thought to result from propagation of the seizure to the limbic system and hypothalamus1. Nocturnal seizure is an independent risk factor for sudden unexpected death in epilepsy (SUDEP)2. Sleep physiology involves the ventrolateral preoptic nucleus of the hypothalamus3. Given the potential overlapping pathways, it is unclear how autonomic dysfunction changes with seizures during sleep. As a result, the main objective of this study is to assess how ictal heart rate (HR) changes between the sleep and awake states. Methods: This retrospective study uses data from patients admitted to the epilepsy monitoring unit at University at Buffalo, from Jan 2015-Jan 2016. This study enrolled patients who had at least one generalized/complex partial seizure occurring in sleep and one while awake. Single lead electrocardiogram (ECG) was analyzed from -60 sec to +120 sec relative to electrographic onset of seizure with HR and beat to beat variability (BBV) averaged over 10 sec intervals. Baseline HR+BBV (30-60sec prior to ictal onset), change in HR+BBV, maximum HR, and time to maximum HR were compared between the awake and sleep states, among all seizures and those with significant HR changes (>20% change) in both states. Results: This study enrolled 14 patients - 38 ictal ECG were analyzed. Significant tachycardia were seen in 20 seizures. No significant bradycardia in data set. There were 7 seizure pairs that had significant tachycardia in both awake and sleep states, during which shows a correlation between BBV percent change (R2 = 0.94) and time to maximum HR (R2 = 0.75, p-value=0.03 compared to rest of seizure pairs), but had variable HR changes (range: -26bpm to 22 bpm in difference between sleep and awake). Significant difference in baseline HR ratio in the patients with significant tachycardia in both states (p-value=0.00012). Figure 1: Percent change of BBV calculated through root mean squared, with percent change during awake seizure on x-axis and percent change during sleep seizures on y-axis. Seizure pairs with significant tachycardia (>20% change) are plotted as orange squares with associated trend line and R2 coefficient, while the other seizure pairs are plotted as blue diamonds.Figure 2: Plot of baseline HR, with baseline HR while awake on x-axis and baseline HR while asleep on y-axis. Seizure pairs with significant tachycardia (>20% change) are plotted as orange squares, while the other seizure pairs are plotted as blue diamonds. Conclusions: Correlation between the BBV and timing suggest a preserved pathophysiology between the awake and sleep states. Ictal tachycardia appeared to be more variable, increasing in some cases, decreasing in others. Patients with significant tachycardia in both states had significantly abnormal baseline HR during sleep.References:Epstein, M. A., Sperling, M. R., & O'Connor, M. J. (1992). Cardiac rhythm during temporal lobe seizures. Neurology, 42, 50-3.Lamberts, R. J., Thijs, R. D., Laffan, A., Langan, Y., & Sander, J. W. (2012, Feb). Sudden unexpected death in epilepsy: people with nocturnal seizures may be at highest risk. Epilepsia, 53(2), 253-7.Saper, C. B., Cano, G., & Scammell, T. E. (2005, DEC 5). Homeostatic, circadian, and emotional regulation of sleep. J Comp Neurol., 493, 92-98. Funding: none